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Study of carbonatation in alkali activated systems
Suchý, Rostislav ; Koplík, Jan (referee) ; Kalina, Lukáš (advisor)
The carbonation of the building materials based on the ordinary Portland cement is relatively well-known and extensively studied phenomenon. Conversely mechanism, reaction products and factors affecting the carbonation of the alkali activated materials are still not sufficiently clarified. In this work, the progression of the carbonation of the alkali activated materials under different conditions was investigated. The reaction products and the microstructural changes were determined by XRD respectively SEM-EDX analysis. The corrosive conditions due to the decreasing of the pH of the binders by the carbonation were observed by XPS analysis of the steel fibers. The carbonation of the alkali activated samples was compared with the reference samples based on the Portland composite cement. Besides these analyzes, the mechanical properties of the binders were monitored.
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Investigation and Modelling of Concrete Carbonation
Rovnaníková, Markéta ; Keršner, Zbyněk (referee) ; Bajza, Adolf (referee) ; Havlica, Jaromír (advisor)
The corrosion of steel reinforcement is probably the most frequent type of degradation of reinforced concrete structures. Reinforcing bars are protected from corrosion by a thin iron oxide layer which is formed on their surface due to a high alkalinity of the surrounding concrete. Corrosion may start when this layer is destroyed (i) either by chloride ion penetration (when the concentration of dissolved chloride at the depth of the reinforcing steel exceeds a critical value) or (ii) by a reduction in the pH value of pore solution to values below 9.5. Such a reduction in alkalinity is the result of carbonation of the Ca(OH)2 in the concrete mass, i.e. of its reaction with the atmospheric CO2. The main aim of this work is an experimental investigation and modelling of carbonation process. The effect of relative humidity, curing period and replacement of Portland cement by supplementary cementing materials (SCM - fly ash, blast furnace slag and metakaolin) on carbonation process has been studied. Calcium hydroxide content in the presence of SCM and their pozzolanic activities have been also determined. Furthermore, lots of parametric studies and comparison of carbonation models have been provided. The software tools based on the introduced models and considering the input data to be statistically independent random variables have been described and used for other parametric studies.
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Durability of repair materials with higher fire resistance for concrete structures
Počekajlo, Václav ; Dohnálek,, Pavel (referee) ; Bydžovský, Jiří (advisor)
This dissertation deals with the study of durability and degradation repair mortars for reinforced concrete structures. In its theoretical part, there are the research findings on the behavior of repair mortars exposed to corrosive environments with different exposure time and selected high temperatures. Processes occurring in repair mortars during their loading at high temperatures or when exposed to chemically aggressive environments are described, We can find recipes designed for cementitious binder based with a specific replacement using slag or fly ash in its practical part. The object of the research was to determine the durability of the proposed repair mortars, and determine their suitability for use on concrete structures, which may be exposed to a synergistic effect of chemically aggressive environments with high temperatures simulating fire.
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Diagnostic properties of concrete exposed to high temperatures
Hudský, Petr ; Sitek,, Libor (referee) ; Bodnárová, Lenka (advisor)
This master’s thesis studies the problems of high temperatures on cement concretes, their following diagnostics from pre-treatment to rehabilitation, the emphasis was on the use of high-speed water jet. In the experimental part of the design of a concrete composition with basalt aggregate. Were reviewed the physico-mechanical properties after thermal loading. The influence of pressure water jet on the thermal load on concrete, pull-off test, the volume of the removed concrete with a strength evaluation and comparison.
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Influence of changes in concrerte pore structure on actually durability of reinforced and pre-stressed structures.
Kovalčíková, Hana ; Adámek, Jiří (advisor)
This master thesis deals with a durability of concrete, which has become the centre of the interests of international scientific insitutes during the last years. The resistence of reinforced concrete depends on the covercrete which the aggresive liquids and gases penetrate through from the environment to reinforcement. According to the ability of the covercrete to penetrate degradative species is possible to tell the durability of concrete constructions. In experimental part we look for the actual state of covercrete, ordinary and high strength, by combination of various experiments. We can find here the test´s results of water and gas permeability and absorbability and sorption of concrete which complete the permeability tests. In final part the impact of different concrete types on durability of reinforced concrete is discussed.
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Nonlinear analysis of load-bearing capacity of reinforced concrete bridge
Sadílková Šomodíková, Martina ; Novák,, Drahomír (referee) ; Lehký, David (advisor)
The subject of master’s thesis is determination of bridge load-bearing capacity and fully probabilistic approach to reliability assessment. It includes a nonlinear analysis of the specific bridge load-bearing capacity in compliance with co-existing Standards and its stochastic and sensitivity analysis. In connection with durability limit states of reinforced concrete structures, the influence of carbonation and the corrosion of reinforcement on the structure’s reliability is also mentioned.
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Lime mortars with the addition of ground limestone
Žižlavský, Tomáš ; Rovnaníková, Pavla (referee) ; Vyšvařil, Martin (advisor)
The thesis is focused on an effect of addition of ground limestone on properties of lime based mortars. Theoretical part of the thesis deals with diferenciation of plasters and their utilization, history of using limestone as an aggregate, its exploitation in the present and its impact on properties of lime based plasters, specially on strenghts. In the next part there's elaborated the carbonation reaction including the influence of external agents. Practical part of the thesis is focused on proving assumtions from theoretical part, particulary on the influence of ground limestone on the strenght properties of lime based plasters.
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